Posted by Alison on 29th February 2008
Vitamin Profile – Vitamin B6 (Pyridoxine)
Pyridoxine can interact with barbiturates, levodopa (1 – dopa, given for Parkinson’s disease), phenytoin (for seizures), isoniazid and cycloserine (used to treat tuberculosis), hydralazine (for hypertension), penicillanime (a treatment for arthritis and Wilson’s disease), oral contraceptives, and vitamin B12.
Pyridoxine supplements may be given to counteract any of the symptoms of vitamin B6 deficiency. However, such symptoms will not be alleviated by pyridoxine unless they are, in fact, caused by Vitamin deficiency.
In addition, pyridoxine has been found to have some therapeutic value for the following conditions.
Depression Associated with Oral Contraceptives
There is limited evidence suggesting that supplemental B6 may be of some value in partially reversing the depression occasionally associated with the use of oral contraceptives. The reason for this is that the estrogenic component of the pill alters blood levels of pyridoxine and therefore increases the daily requirement. Pyridoxine is needed to form brain neurotransmitters, and it also binds weakly to steroid hormone receptors.
Large-scale controlled trials are lacking to confirm this observation. However, we recommend B6 supplementation in doses of 25 to 100 mg per day for those women taking oral contraceptives who have experienced troublesome depression and not achieved relief from another therapy. Since this depression is specifically caused by B6 deficiency, vitamin B6 therapy should not be viewed as of general value in the treatment of any other form of depression.
Vitamin B6 has also received publicity as a treatment for this common problem. The theory here is that the symptoms of premenstrual syndrome (PMS) are caused by a hormone imbalance associated with menstruation. Advocates of this therapy say that the situation is similar to oral contraceptive-related depression and the marginal deficiencies reported among pregnant women. Another possible mechanism of action may be the ability of high doses of B6 to bind to steroid hormone receptors. In any event, there have been at least five small, randomized, placebo-controlled trials addressing the question of the usefulness of B6 to relieve PMS. We can summarize the evidence by simply indicating that the results are not in agreement. Most studies show a small improvement with B6 compared to placebo, and some women claim significant relief from PMS with B6.
Our advice: B6 may be worth a try if PMS is a problem. A dose of 100 to 200 mg per day (100 mg twice a day) should be used, but do not take over 200 mg per day due to toxicity risks. Take the B6 only during the two weeks prior to menses, that is, during the time when PMS occurs. If after a test of one or two cycles it does not seem to be helpful, stop its use. B6 seems to work only for some women, not all, and one cannot predict who will benefit and who will not.
Reduction of Breast Milk
Some European physicians have employed daily doses of 50 mg of pyridoxine to purposely suppress prolactin secretion and reduce milk re¬production in women who have just given birth. High-dose pyridoxine has been hailed as a savior because it may replace the hormones that have been used for this purpose. There is not much information to support this use of B6.
Treating Inborn Errors of Metabolism
There are at least six rare, inherited genetic defects that can be treated by giving high doses of vitamin B6. Studies have shown that in most cases these defects are the result of a genetic error that leads to the manufacture of a defective enzyme. The defect is usually related to the enzyme’s inability to bind tightly to its needed vitamin. If the enzyme cannot bind to the vitamin, it can not function. Extraordinarily high vitamin doses may be able to “flood” the enzyme, so even though the vitamin is not tightly bound to the enzyme, it can still work.
These are not true vitamin-deficiency diseases. They are defects in a single enzyme that can be overcome by megadoses of the appropriate vitamin. The abnormally low enzyme activity can lead to a variety of symptoms, but usually the problem is revealed during early childhood in the form of mental retardation and failure to grow and thrive.
There are several examples of B6-dependent inborn errors of metabolism. These rare but serious defects often respond seemingly miraculously to vitamin treatment. It must be emphasized that most cases of mental retardation or developmental problems will not respond to vitamin treatments. Only a specialist can pinpoint cases that will respond and the exact vitamin needed.
Carpal Tunnel Syndrome
The sheath of tissue that carries the tendons and the median nerve through the wrist to the hand is called the carpal tunnel, and for unknown reasons, the size of the opening can become reduced. When this happens, the nerves passing through become compressed, with resulting pain, loss of touch sensation, loss of strength, and tingling sensations in the hand. Carpal tunnel syndrome can accompany several disease states, but more commonly it appears as a result of repetitive motions of the hand and wrist. It is frequently seen in data entry personnel, carpenters, joiners, violinists, and writers, for example. Pain at night interferes with sleep, and loss of strength in the hand sometimes makes work impossible. The only sure treatment is surgery to open up the tunnel and to relieve pressure.
One well-known research group in Texas has published numerous reports on the successful use of vitamin B6 to relieve carpal tunnel syndrome. They believe that carpal tunnel syndrome is related to vitamin B6 deficiency. However, the published experiences of other investigators have not been so enthusiastic about the value of B6 treatment. More recent clinical trials have indicated that B6 therapy relieves pain to some extent but may not improve nerve conduction function. This implies that the B6 is affecting pain thresholds and may not be doing much to improve the underlying reason for the pain. Thus inflammation and damage may be continuing, but you don’t feel the pain as much.
B6 therapy should be undertaken only with the guidance of a health care professional experienced in dealing with carpal tunnel syndrome. Doses of B6 should be 100 to 300 mg per day and continue for at least three months. This is about two hundred times the RD A value. If signs of toxicity develop (numbness in the legs, for example), discontinue use immediately.
Relieving Morning Sickness
Pyridoxine has been combined with an antihistamine and promoted for the treatment of morning sickness. This combination was called Benedectin and was sold in the United States for almost two decades until it was withdrawn in 1982. The withdrawal was a voluntary action on the part of the manufacturer because the question was raised of this product’s potential for causing birth defects. High doses of pyridoxine have caused birth defects in laboratory animals, and while this lab data can not be directly translated to human beings, Bendectin was with-drawn because of the manufacturer’s desire to avoid adverse publicity and the staggering cost of potential lawsuits. Thus, the issue was never resolved to anyone’s satisfaction. There is evidence to support the role of pyridoxine in the treatment of morning sickness. But we recommend mat pregnant or breast-feeding women take pyridoxine only for nutritional purposes, unless it is taken under medical guidance.
In addition, there is nothing to indicate this vitamin is valuable in treating nausea and vomiting caused by conditions other than pregnancy.
Water-Soluble Vitamins: Vitamin B,,
In recent years, elevated blood levels of an amino acid called homocysteine have been associated with a higher risk of heart disease and blood vessel disease (atherosclerosis). Pyridoxine is one of three vitamins (the others are B12 and folic acid) that are involved in getting rid of homocysteine in the body. RDA levels of vitamin supplements will usually normalize homocysteine levels. Our message is simple: Take a multivitamin/mineral supplements that contains 100 percent of the RDA for B6, B12, and folic acid. Unless you have a rare inborn error of metabolism, this will keep homocysteine levels at an appropriate value.
We cannot recommend that you take vitamin B6 to treat arthritis, diabetes, mental retardation, numbness, or obesity. B6 will also not prevent aging, fluid retention, or leg cramps, nor can it improve — your vision or help you lose weight.
Vitamin B6 has been used to treat a variety of mental disorders, including childhood learning disabilities, autism, schizophrenia, and Alzheimer’s disease. The evidence for value of B6 here is conflicting and inconclusive. Low levels of B6 have not been found in mental disease patients.
Vitamin B6, as pyridoxine hydrochloride tablets, can be purchased without a prescription in strengths between 25 and 100mg. Several timed-release preparations are also available, but the value of timed-release vitamins is questionable. Pyridoxine hydrochloride (100 mg) injection is available only on a doctor’s prescription.